Spies J.R. and Chambers D.C., 1950, Determination of tryptophan with p-dimethylaminobenzaldehyde using photochemical development of color, Anal. Chem., 22: 1209

Tatár E., Khalifa M., Záray Gy. and Molnár-Perl I., 1994, Comparison of the recovery of amino acids vapor phase hydrolyzates proteins performed in the Pico Tag™ Work Station and in the CEM microwave apparatus,/Chromatogr., 672: 109